Surface design of nanostructured catalysts for energy and environmental uses

<p>For development of new efficient catalysts for energy and environmental uses, designs of “active sites", "reaction fields" and “energy injection” are essential factors. In the nanospace of zeolite, mesoporous silica and metal-organic framework (MOF), it is possible to control the structure of catalytic active sites in forms of fine particles, clusters, molecules, and atomic moieties, and also possible to control the reaction fields with unique properties such as hydrophobicity and electrostatic fields. Ultrafine semiconductor photocatalysts, single-site photocatalysts, plasmonic catalysts, and MOF photocatalysts, can be designed for H₂ production-storage-transportation, CO₂ fixation, H₂O₂ synthesis, and various environmental reactions.</p><p></p><p>Ultrafine semiconductor: Hybrid of TiO₂ photocatalyst and porous adsorbent can decompose organic pollutants diluted in air and water efficiently by adsorbing them. In particular, the cavities of the hydrophobic porous material are effective in adsorbing dilute organic compounds and promoting the photocatalytic performance.</p><p></p><p>Single-site photocatalyst: The tetrahedrally coordinated metal oxide (titanium, chromium, vanadium, and molybdenum oxide) moieties can be implanted and isolated in the silica matrixes of microporous zeolite and mesoporous silica materials and named “single-site photocatalysts”. Under light irradiation these single-site photocatalysts form the charge-transfer excited state, i.e., the excited electron-hole pair state which localizes quite near to each other, plays a significant role in various photocatalytic reactions. Photofunctional metal complex capsulated within nano-cavities can also perform as single-site photocatalyst with high activity and selectivity.</p><p></p><p>Plasmonic catalyst: Design of nanostructured plasmonic catalysts, such as nanoparticles and nanosheet morphologies, that strongly absorb visible light over a wide range of the solar spectrum due to localized surface plasmon resonance (LSPR) have been designed. A method for the synthesis of Ag nanoparticles with color dependent on the particle size and morphology, was developed with combined microwave heating and mesoporous silica materials. Plasmonic materials based on earth abundant elements found that reduced molybdenum oxide (H_xMoO_3-y) nanosheet with oxygen defects and doped hydrogen displayed intense absorption in a wide range from the visible to the near-infrared region.</p><p></p><p>MOF photocatalyst: Our group demonstrated that application of MOF materials for photocatalytic H₂O₂ production via oxygen reduction for the first time. MOF constructed from metal clusters and organic linkers offer opportunities to develop novel materials due to the advantages, such as porosity, versatility, and structural diversity. With the advantages of the unprecedented flexibility of MOF, we designed the MOF materials to improve the photocatalytic activity for H₂O₂ production by the linker functionalization, the missing-linker defects in the MOF frameworks, and the utilization of a noble two-phase reaction system using hydrophobic MOF.</p><p></p><p>[1] T. Zhang, H. Yamashita, Y. Zhao, et al., JACS Au, 2023, 3, 516.</p><p>[2] Y. Kondo, H. Yamashita, et al., Chem, 2022, 8, 2924.</p><p>[3] Y. Wen, H. Yamashita, Y. Zhao, et al., Angew. Chem. Int. Ed., 2022, 61, e202205972.</p><p>[4] Y. Chen, H. Yamashita, Z. Bian, et al., Angew. Chem. Int. Ed., 2022, 61, e202213640.</p><p>[5] H. Yin, H. Yamashita, et al., Angew. Chem. Int. Ed., 2022, 61, e2021114242.</p><p>View PDF for the rest of the abstract.</p>